In a communication system, in order to reduce costs of network construction and operation, areas required to be monitored and optimized are tested through manual works in a traditional drive test, based on an evolution of the next generation network, dependency on the traditional drive, test is lessened, and more intelligent network optimization tools are necessary, thus a requirement of automatically collecting measurements of a terminal and minimizing a manual drive test is extremely beneficial. On the other hand, optimization can be performed automatically and a network operation can be understood comprehensively by using test results of a User Equipment (UE). Therefore, a technical research of Minimization of drive test (MDT) is put forward in the Long Term Evolution (LTE) system, and meanwhile the technique also can be applied in a Universal Mobile Telecommunications System (UMTS). An implementation way is based on a measurement control and reporting mechanism under an eNB, and after the measurement, the UE performs a report which mainly includes two types of report such as an immediate report in a connection state and a log report in an IDLE state and also can include a log report type in the connection state.
Currently, a measurement content of the MDT mainly includes the following types. 1) Periodical downlink pilot measurement: Le, a measurement in a wireless environment, such as CPICH RSCP, CPICH Ec/No, RSRP and RSRQ (only to a connection mode) are recorded periodically.
This measurement log corresponds to a user example of coverage optimization.
The operators realize that main measurements for the throughput which can be implemented by the Downlink (DL) coverage are a DL common pilot receiving level and a DL Signal to Interference Ratio (SIR) level. Configurations of the existing Radio Resource Management (RRM) measurement mainly depend on a measurement report and a periodical report of event triggering, however certain limitations also exist:
A. There is no accompanying location information, even though the operators can identify a cell through a DL coverage, the operators are still required to execute the drive test to determine problematic areas in the cell, since accurate location information can be detected by a low DL common pilot receiving level or a low SIR level, it cannot be obtained from the current RRM mechanism.
B. The existing RRM mechanism only permits the measurement report when the UE is connected to a specific cell and there is sufficient Uplink (UL) coverage for transmitting the measurement report. This will limit the measurements collected from the UE, and the UE cannot experience an RLF and sufficient UL coverage.
2) Signal quality of a Serving Cell becomes worse than a threshold: when a signal quality of a serving cell is worse than a configured threshold, wireless environment measurements such as CPICH RSCP, CPICH Ec/No, or TDD P-CCPCH RSCP and ISCP, RSRP and RSRQ (only to a connection mode) are recorded. A measurement log window is needed to collect information within a certain period of time after and before the event occurs.
The measurement log corresponds to the user example of coverage optimization.
If the operators are interested in a specific DL coverage problem, it is effective to adopt measurement logs corresponding to the interested problem. The operators can convert their criterions (e.g. outside the coverage) into thresholds in order to find the problematic areas. In order to be able to identify characteristics of the problem (e.g. occurring in a specific mobile scenario), a beneficial measurement log thereof provides the information.
3) Transmit power headroom becomes less than a threshold: when transmit power headroom of the UE becomes less than a configured threshold, the transmit power headroom and wireless environment measurements such as CPICH RSCP, CPICH Ec/No, or TDD P-CCPCH RSCP and ISCP. RSRP and RSRQ (only to a connection mode) are recorded, and this measurement log corresponds to the user example of coverage optimization.
By observing a level of a UL transmit power, the operators can detect link budgets which have not sufficient UL, and also can deduce a realizable UL throughput level in the network. Collecting such information can assist the operators to better adjust Cell individual Offset (CIO), thereby deciding a layout in a center cell of the network and adjusting antenna dip angles and so on.
4) Random access failure: when a random access failure occurs, detailed information about the random access and wireless environment measurements such as CPICH RSCP, CPICH Ec/No, or TDD P-CCPCH RSCP and ISCP, RSCP and RSRQ (only in a connection state) are recorded.
This measurement log corresponds to the user example of coverage optimization.
Reasons for the random access failure are such as an inaccurate transmit power setting or competition. The operators can collect information about the random access failure to analyze characteristics of the random access failure. DL wireless environment measurements such as CPICH RSCP, CPICH Ec/No, RSRP and RSRQ are also necessary, for the open-loop power control in a random access process depends on these characteristics. Collecting such information can assist the operators to better adjust random access parameters and to adjust antenna dip angles and so on.
5) Paging Channel failure: when the UE does not decode a Physical Control Channel (PCCH) in a paging channel during a continuous time to X2, detailed information of wireless environment, location information, time and cell identifier are recorded, even though the operators can decode a Physical Downlink Control Channel (PDCCH) in a paging moment.
This measurement log corresponds to a user example of common channel parameterization.
In the IDLE mode, with regard to the operators, whether the UE can be paged reliably is extremely important. If a user cannot be paged, it will exert a negative influence on the user experience (at least in a paging unit) and also have an influence on incomes of the operators (missing the opportunities for calling). In the current network, the drive test can be used for estimating a capability of the UE by receiving paging message in a cell coverage area. Since these actions will cause high costs, if the UE can record an occurrence time when the UE cannot decode the information on the paging channel and other related information, it is very beneficial.
6) Broadcast Channel failure: when the UE does not find a related DL common channel to obtain system message required for residing in a cell, message information, location information, time, cell identifier and frequency in a wireless environment are recorded. This measurement corresponds to user examples of the coverage and capacity optimization and the common channel parameterization.
7) Radio Link Failure report (RLF report): when an RLF occurs in the UE, the UE reports wireless measurements such as CPICH RSCP, CPICH Ec/No or TDD P-CCPCH and ISCP, RSRP and RSRQ. A measurement for the RLF Report corresponds to the user example of coverage optimization.
The RLF report can identify a plurality of problems coming from a coverage aspect. Therefore, in an actual network, a probability of detecting coverage holes through this measurement information is expected to be high, and certain problems normally related to a detection of the DL common channel are also caused by the coverage problem. The RLF report provides a method for solving basic DL coverage problems, specific measurements for the common channel parameterization can be concentrated on adjusting the common channel parameters.
Collecting such information can assist the operators to find the coverage problems in the specific areas, thus reducing the manual drive tests.
At present, with regard to MDT configuration information, contents are also different according to the two different types (i.e. an immediate report type and a log report type), including: an MDT application scope which can be represented as a cell list or a Tracking Area (TA) list, identifier information of UE (only used for tracking based on the UE in the UMTS), and a MDT measurement content; with regard to an immediate reporting mode, it is also required to include a report trigger event, a report interval and a report amount; and with regard to a log reporting mode, a log record interval and a log configuration duration are included.
Meanwhile, analogy can be performed between an MDT flow and a current signaling tracking flow, and there are two basic ways: one is an MDT flow based on management; and the other is an MDT flow based on signaling. For the latter, Operation Administration and Maintenance (OAM) will send the mar configuration information to a Home Subscriber Server (HSS), the HSS can select an appropriate UE, when the UE performs a location update through an ATTACH flow, a core network will send the MDT configuration information to the eNB through an S1 interface flow, the eNB can manage the MDT configuration information locally, meanwhile, since the eNB also knows more state information of the UE, such that the eNB can decide whether it is appropriate for the UE to perform corresponding MDT measurements currently according to certain local information in combination with the MDT configuration information sent by the core network, and if it is appropriate, the configuration information is sent to a corresponding UE through an air interface, and the UE will perform measurement report according to the MDT configuration information.
However, a scheme of how to perform an MDT configuration information interaction between the core network and the base station for implementing the drive test hasn't been proposed at present.